C++Do/While Loop
The Do/While Loop
Thedo/while loop is a variant of thewhile loop. This loop will execute the code blockonce, before checking if the condition is true. Then it will repeat the loop as long as the condition is true.
Syntax
// code block to be executed
}
while (condition);
Note: The semicolon; after thewhile condition is required!
Do/While Example
The example below uses ado/while loop. The loop will always be executed at least once, even if the condition is false, because the code block is executed before the condition is tested.
Do not forget to increase the variable used in the condition (i++), otherwise the loop will never end!
Condition is False from the Start
In the example above, the conditioni < 5 wastrue at the beginning, so the loop executed multiple times. But what if the condition isfalse right from the start?
In the example below, the variablei starts at10, so the conditioni < 5 is false immediately - yet thedo/while loop still runs once:
Summary
Thedo/while loop always runs at least once, even if the condition is already false. This is different from a regularwhile loop, which would skip the loop entirely if the condition is false at the start.
This behavior makesdo/while useful when you want to ensure something happens at least once, like showing a message or asking for user input.
Practical Example: User Input
This example keeps asking the user to enter a positive number. The loop stops when the user enters 0 or a negative number:
Example
do {
cout << "Enter a positive number: ";
cin >> number;
} while (number > 0);
